1. Field of the Invention
The present invention relates to a method of displaying sections of a digital map database, which are pictures or images of real geographic areas, the digital map database containing data regarding respective geographic elements. The present invention also relates to a digital map database, which is a representation of real geographic areas and which contains data regarding geographic formations and respective attributes for corresponding geographic elements. The present invention also relates to an operating unit of a navigation system with a display device for displaying sections of a digital map database, which are pictures or images of real geographic areas. The present invention relates further to a navigation system for a vehicle, especially a motor vehicle, with a navigation module, which makes a digital map database available, and with an operating unit connected with the navigation module, which has a display device for display of sections of the digital map database, especially for performing the above-mentioned process. In addition, the invention relates to an interface between a digital map database, which is a representation of real geographic areas and contains data of geographic elements, and to a display device for displaying sections of the digital map database.
2. Prior Art
Permanently installed navigation systems guide an operator of a vehicle, especially a motor vehicle, aircraft or ship, rapidly, simply and reliably to a desired destination, without requiring the operator to acquire and study map materials and arduously plan a route. For that purpose suitable navigation data, for example based on chart data, land map data or street map data, is available in the navigation system, for example, stored on CD-ROM as a digital map database. The navigation system uses, for example, a GPS (Global Positioning System) to ascertain its present location in order to calculate navigation advisory messages, which guide the operator to his or her destination. The navigation data includes, for example, data regarding streets and roads for a motor vehicle as well as geographic information, such as data regarding mountains, oceans, woods, cultivated regions, buildings or other topographic elements, or additional information, e.g. such as data regarding restaurants, hotels, worthy sites or the like.
The digital map database is essentially a representation of a real street network and a suitable geographic region. This information from the digital map database is displayed on a display device in an operating unit in order to inform the operator. The number of geographic features and the degree of detail appearing in the display is selected differently to obtain an easy-to-read, clear display in different situations. For example, only major highways are shown on an overview map. Residential street maps should contain details up to residential buildings. The selection of the map features to be displayed substantially effects the readability and visibility of map sections displayed on the basis of a digital map database. This selection of features for display is especially important for maps displayed in a vehicle, since an operator of the vehicle must be able to ascertain all required information for route guidance with as brief as possible a glance at the display device. The map display significantly cannot be set up according to a generally established rule, but a relative importance should be assigned to the different displayed elements. For example, an overview map of the Ruhr region may significantly contain only expressways or major highways. A map of Arizona in the same scale could also contain, in contrast, comparatively smaller roads.
In navigation systems for a motor vehicle it is significant that the navigation module, which accesses the digital map database is separate from the display device and is also displayed separately. Thus the navigation module requires a predetermined interface for accessing the digital map database. This interface must permit setting up a digital map in different scales on the display device that has sufficient clarity.
The interfaces for navigation systems are, for example, made by NAVTECH or ETAK Inc.. These interfaces provide access to the physical memory format of the digital map database. Generally different types of digital map databases are used in different vehicles. Furthermore access conflicts can occur during access by the navigation module, for example for internal route computation, and operating unit processing, for example for production of a display of sections of the digital map database on the display unit. Furthermore the elements contained in the digital map database are described as xe2x80x9cdirectxe2x80x9d, i.e. a highway or expressway is described as a street of the class xe2x80x9cmotorwayxe2x80x9d with a number. However it has been shown that standardization and agreement regarding classification of map elements is possible only to a very unsatisfactory degree which is unsuitable for display purposes.
It is not possible to perform an optimized pre-calculation of the important displayed elements for the respective display screen sections in the digital map database for every possible zoom stage and every possible display. Thus the operating unit must include means for deciding which elements should be shown and which elements should be suppressed during production of the display. The possible overlap of the displayed elements is an additional difficulty, which can occur, for example, with an island in an ocean. Also the relative overlap must be detected in the interface. Furthermore height or elevation information is generally not contained in the digital map database of a vehicular navigation system.
With the standard xe2x80x9cdirectxe2x80x9d or absolute coded digital map according to the state of the art it is disadvantageous that the thinning out algorithms computed in the display device are operational only with certain physical data formats known in detail.
It is an object of the present invention to provide an improved method for displaying sections of a digital map database in a navigation system in a vehicle, which does not have the above-described disadvantages and which dynamically adjusts the display of the sections of the digital map database, i.e. to the respective actual requirements.
It is another object of the present invention to provide an improved navigation system with an improved operating unit for performing the improved method of displaying sections of a digital map database, which does not have the above-described disadvantages and which dynamically adjusts the display of the sections of the digital map database.
It is a further object of the present invention to provide an improved interface of the above-described type and an improved operating unit of the above-described type of the navigation system for performing the improved method.
It is an additional object of the present invention to provide an improved digital map database for the improved method of displaying predetermined sections of the database in a navigation system in a vehicle, which does not have the above-described disadvantages and which dynamically adjusts the display of the sections of the digital map database.
According to one aspect of the present invention the method of displaying a predetermined section of the digital map database, which represents a real geographic area, on a display device, the digital map data based containing map data representing geographic elements, includes
a) selecting respective geographic elements for display according to the predetermined section of the digital map database to be displayed; and
b) determining whether the respective geographic elements selected in step a) are associated with corresponding display-priority-determining attributes; and
c) evaluating the display-priority-determining attributes of the respective geographic elements having the display-priority-determining attributes in the predetermined section to determine whether they should be actually visible in the display device, or not.
Furthermore the above-described method provides the advantage that an optimum xe2x80x9cthinning outxe2x80x9d of the displayed information occurs for the display screen contents for display of the predetermined section of the digital map database. The clarity of the instantaneous display is thus adjusted for various different views, e.g. by means of an algorithm.
Preferred embodiments of the method according to the invention have additional advantages.
According to preferred embodiments of the method a limiting value for the display-priority-determining attributes of the respective geographic elements to be actually displayed is dynamically established. The number of the geographic elements actually coinciding with the predetermined section determines this limiting value. Alternatively, the scale of the predetermined section determines the limiting value.
In preferred embodiments of the method respective value ranges for the display-priority-determining attributes of the geographic elements that determine whether or not the geographic elements are displayed or not are set up for the predetermined section to be displayed. Thus the method, for example, can display only expressways or major highway roads on the display device in the Ruhr region of Germany, while also displaying streets and roads with lower values of the display-priority-determining attributes on the display device in Arizona.
When relative overlap parameters (Z-level) are attributed to the respective geographic elements and the respective geographic elements are added to the predetermined section to be displayed one after the other in order of sequentially increasing relative overlap parameters, a realistic view of a geographic area can be preferably produced in spite of the absence of height information in the digital map database. For example an island can have a higher Z-level than the surrounding water. The water is then added to the predetermined section first and then the island is shown. Because of this aspect of the preferred embodiments of the method it is guaranteed that the island will be visible and not covered by the water.
The display-priority-determining attributes are either already associated with the geographic elements in the digital map database or in an interface connecting the digital map database and the display device.
The respective values of the display-priority-determining attributes of the geographic elements are preferably employed according to their relative magnitudes and not their absolute values.
According to another aspect of the present invention a digital map database is provided that represents real geographic areas. This digital map database includes data regarding respective geographic elements and corresponding attributes associated with the respective geographic elements. At least one part of the geographic elements is provided with respective additional display-priority-determining attributes defining corresponding display priorities for each of the at least one part of the geographic elements. The additional display-priority-determining attributes establish whether or not the geographic elements in the section of the digital map database to be displayed are actually visible or not on the display device.
The digital map database according to the invention has the advantage that an optimum xe2x80x9cthinning outxe2x80x9d of the visible information in the predetermined section to be displayed on the display device occurs. The clarity of the instantaneous display is thus adjusted for various different views, e.g. by means of an algorithm.
Advantageous features of the digital map database are provided in preferred embodiments.
Different parts of the digital map database can be thinned out differently for display by providing predetermined selection rules for the display-priority-determining attributes of the respective geographic elements that are associated with the respective different parts of the digital map database. The selection rules establish respective value ranges for the display-priority-determining attributes that determine whether or not the geographic elements in the predetermined section are visible on the display device. For example, then only expressways or major highway roads can be shown on the display device in the Ruhr region of Germany, while also streets and roads with lower values of the display-priority-determining attributes can be shown on the display device in Arizona.
A realistic display can be produced in spite of the omission of height information in the digital map database when relative overlap parameters (Z-level) are attributed to the respective geographic elements in the digital map database. If the respective geographic elements in the predetermined section are now made visible on the display device in order of increasing Z-level, the above-mentioned realistic reproduction of the appearance of a selected geographic area is produced. For example, if an island has a higher Z-level than the surrounding water, then the island will be shown after the water. Thus it is guaranteed that the island it will not be covered or obscured by the water.
According to another aspect of the present invention an operating unit is provided that includes means for evaluating display-priority-determining attributes of the respective geographic elements. The means for evaluating display-priority-determining attributes of the geographic elements establish whether the respective geographic elements in the predetermined section are visible in the display, or not. This determination is made according to the predetermined section of the map database to be displayed and according to the display-priority-determining attributes.
This feature of the operating unit has the advantage that an optimum xe2x80x9cthinning outxe2x80x9d of the display screen contents for display of the predetermined section of the digital map database occurs. Thus the clarity of the instantaneous display is adjusted for different views, for example by means of a suitable algorithm.
Preferred embodiments of the operating device have various additional advantages.
In a preferred embodiment of the operating device according to the invention the means for evaluating display-priority-determining attributes includes means for determining a limiting value for the display-priority-determining attributes of the respective geographic elements to be actually displayed dynamically. This limiting value depends on the number of the geographic elements in the predetermined section of the map database or on the scale of the predetermined section, so that only those geographic elements in the predetermined section having display-priority-determining attributes above the limiting value are actually displayed.
A different thinning out for different parts of the map database can be produced when the means for evaluating display-priority-determining attributes includes means for associating respective value ranges of the display-priority-determining attributes with displaying the geographic elements in the predetermined section visible, or not, on the display device. For example, then only expressways or major highway roads can be shown on the display device in the Ruhr region of Germany, while also streets and roads with lower values of the display-priority-determining attributes can be shown on the display device in Arizona.
A realistic display can be produced in spite of the omission of height information in the digital map database when relative overlap parameters (Z-level) are attributed to the respective geographic elements in the digital map database. If the respective geographic elements in the predetermined section are now made visible on the display device in order of increasing Z-level, the above-mentioned realistic reproduction of the appearance of a selected geographic area is produced. For example, if an island has a higher Z-level than the surrounding water, then the island will be shown after the water. Thus it is guaranteed that the island it will not be covered or obscured by the water.
Furthermore the navigation system of the above-described kind for performing the method according to the invention contains the above-described digital map database and the operating unit.
These features provide the advantage that an optimum xe2x80x9cthinning outxe2x80x9d of the visible information in the predetermined section to be displayed on the display device occurs. The clarity of the instantaneous display is thus adjusted for various different views, e.g. by means of an algorithm.
Various advantages are provided by preferred embodiments of the navigation system according to the invention.
In a preferred embodiment the navigation system includes a navigation module that stores the digital map database on a data-recording medium or that retrieves currently required data from a digital map database by means of a data connection, especially a radio connection, from a location outside of the navigation system.
Means for incorporating and retaining actual traffic information in the data taken from the digital map database for navigation, especially by means of RDS-TMC, is preferably provided in the navigation system for consideration of the actual continuously changing traffic situation for display and route calculation.
According to another aspect of the present invention an interface is provided that connects a digital map database and display means for displaying a predetermined section of the digital data base representing actual geographic areas and containing data regarding the respective geographic elements. The interface includes means for associating corresponding display-priority-determining attributes with the respective geographic elements during transfer of map data from the digital map database to the display means. The display-priority-determining attributes establish whether or not individual respective geographic elements in the predetermined section of the digital database are made visible or not in the display means in accordance with the predetermined section to be displayed.
This has the advantage that an optimum xe2x80x9cthinning outxe2x80x9d of certain display screen contents for display of the predetermined section of the digital map database takes place. The clarity of the instantaneous display is thus adjusted for various different views, e.g. by means of an algorithm.
This interface preferably includes means for connecting an operating unit of the display means and a navigation module of a navigation system with each other.
The geographic elements include, among others, streets and roads for motor vehicles, mountains, oceans, woods, buildings, restaurants, hotels or sites. The attributes of the geographic elements include, for example, travel direction, speed or street signs for the streets and roads. Furthermore the geographic elements of the digital map database are appropriately stored as data on a data-bearing medium, especially a CD-ROM.